Yes, the bank will apply for enforcement, but you can negotiate with the bank to continue repayment. Generally, banks don't go too far. They want money, not life.

Second, what should I do if I don't pay back the car loan?

If you don't have the money to repay the loan and buy a car, you can apply to the lending institution for deferred repayment first, or borrow money from your family and friends for repayment. Don't be overdue if you can pay back the money. Car loans are generally on credit. If it is overdue, you will have a bad credit record, which will affect your future card loans, and this record will be deleted five years after you pay off your debts, which has a great impact. Moreover, there will be liquidated damages, penalty interest and other expenses after loans overdue, so it is recommended to repay the loan on time.

Third, what should I do if I help others get a loan to buy a car and still don't pay?

You're the only one who paid back the money. The bank only recognizes whose loan. If the bank fails to pay you back three times, you will bear legal responsibility, that is, you will be arrested. Besides, you will never hang out in the bank again, and you can't lend money to your son and brother.